1. Field of the Invention
The present invention relates to an electrophotographic photosensitive member, a process cartridge, and an electrophotographic apparatus.
2. Description of the Related Art
In the electrophotographic field, there have recently been advances in improvement in image quality typified by colorization. Colorization increases the number of halftone images and solid images, which are required to have better image quality. For example, in an electrophotographic apparatus using reversal development, when image formation in which a portion irradiated with light is responsible for a halftone image in a subsequent rotation is performed in one image, a phenomenon (positive ghost phenomenon) in which the image density of only the portion irradiated with light is increased is liable to occur.
Examples of an electrophotographic photosensitive member include an electrophotographic photosensitive member having a structure in which a charge-generating layer containing a charge-generating substance (organic photoconductive substance) and a hole-transporting layer containing a hole-transporting substance are provided on a conductive support; and an electrophotographic photosensitive member having a structure in which a photosensitive layer (photosensitive layer having a single-layer structure) containing a charge-generating substance and a hole-transporting substance is provided on a conductive support.
In the case where the photosensitive layer is just provided on the conductive support, hole injection can occur from the conductive support to the photosensitive layer when a voltage is applied to the electrophotographic photosensitive member. The hole injection from the conductive support to the photosensitive layer causes black-spot-like image defects (hereinafter, referred to as “black spots”), significantly reducing the image quality. To overcome the foregoing problems, a method is employed in which an electrically blocking intermediate layer is provided between the photosensitive layer and the conductive support.
However, at an excessively high electrical resistance of the intermediate layer, electrons generated in the charge-generating layer are accumulated in the photosensitive layer to cause a ghost phenomenon. Thus, the electrical resistance of the intermediate layer needs to be reduced to some extent. It is necessary to achieve a good balance between the suppression of the formation of a ghost image and the suppression of black spots.
To suppress the accumulation of electrons in the photosensitive layer and produce an electrophotographic photosensitive member that suppresses the formation of a ghost image, a method is employed in which surface-treated metal oxide particles are incorporated into the intermediate layer. Japanese Patent Laid-Open No. 3-013957 discloses that metal oxide particles surface-treated with an organic titanium compound are incorporated into an intermediate layer. Japanese Patent Laid-Open No. 2005-292821 discloses that metal oxide particles surface-treated with a sulfur atom-containing reactive organic compound are incorporated into an intermediate layer. Japanese Patent Laid-Open No. 9-151157 discloses that the use of an electron-transporting substance allows electrons in a photosensitive layer to flow to a conductive support.
However, even if the surface-treated metal oxide particles or the electron-transporting substance is used, a high-level balance between the suppression of the formation of a ghost image and the suppression of black spots is not achieved.